The R-T-B based permanent magnet (R represents a rare earth element, and T represents Fe or Fe with part of it replaced by Co) comprising a tetragonal compound R2T14B as the major phase is known to have excellent magnetic properties, and has been considered as a representative permanent magnet with good performances since it was invented in 1982 (Patent Document 1: Japanese Laid-Open Patent Publication No. Sho 59-46008).
In particular, the R-T-B based permanent magnets in which the rare earth element R consists of Nd, Pr, Dy, Ho or Tb have large magnetic anisotropy fields Ha, and are widely used as permanent magnet materials. Of those, the Nd—Fe—B based permanent magnet having Nd as the rare earth element R is widely used in people's livelihood, industries, transportation equipment and the like, because it has a good balance among saturation magnetization Is, curie temperature Tc and magnetic anisotropy field Ha. However, the use of the R—Fe—B based permanent magnet has become wider and wider in recent years, causing a rapid increase in the consumption of Nd or Pr and the like. Thus, Nd or Pr and the like as the precious resource is required to be effectively used and the material cost of the R—Fe—B based permanent magnet is required to be lowered.
In another respect, there is a problem that the R—Fe—B based permanent magnet requires a large amount of energy for the crystallization. Further, there is also a problem that, if a thermal treatment is provided at a high temperature to perform the crystallization, the magnetic properties will be deteriorated due to the mix of impurities from surrounding environment. In this respect, it is required that the R—Fe—B based permanent magnet can be crystallized at a low temperature.